Paper machines and paper board machines are used for forming web-like material, such as paper or paper board, running continuously through the machine. The web running in paper machines has to be monitored in order to detect possible faults in the paper or paper board web and to achieve good quality in the final product. Normally, web break cameras of web monitoring systems are installed in various beams or beam structures extending below, above, or by the side of the web. From above the web, the cameras monitor the quality of the web, for example, via openings or windows in the beams or beam structures. However, the quality of images produced by a camera belonging to a web monitoring camera system placed in a beam structure may be affected by splashes in paper and paper board machines, blurring the monitoring windows or camera lenses. The soiling makes it difficult to detect faults in the web. However, the quality of the web has to be controllable in order to meet the strict quality specifications set by customers.
At present, it is necessary to perform manual washing of the lenses, or the structures protecting the lenses, for example transparent covers, of the cameras in beams and beam systems when they become soiled, so that the soiling would not impair the quality of the image material recorded by the cameras. Alternatively, a washing liquid spray may be provided in front of the lenses, on the outside. In addition to or instead of the washing, the lens protecting structures can be cleaned by blowing compressed air or compressed gas. Upon blowing, the compressed air/gas is directed to pass in front of the lens protecting structures so that the dirt is removed by the stream of compressed air/gas along the lens or the structures, making imaging of better quality possible. Alternatively, the air can be blown into the camera where it flows along the side of the camera, cooling down the camera, and further past the lens, making it clean, and exiting the camera through the pinhole.